Unexplained intestinal dysfunction is common in HIV-infected individuals with or without AIDS. Previous studies demonstrated variation in the expression of HIV antigens and RNA during disease progression, and associations with histopathologic alterations, clinical symptoms, and immune alterations. The changes were greatest in HIV-infected individuals without AIDS. We hypothesize that intestinal mucosa is a preferred reservoir for HIV and a site where lymphocytes become infected and are destroyed. The process is chronic and self-perpetuating due to the proximity of bacterial and other foreign antigens and to the altered release of cytokines which modulate HIV replication. However, the pathogenic importance of this process is not well defined. The aims of this proposal are to determine the cellular reservoirs and content of HIV DNA and RNA in intestinal mucosa, to determine if mucosal HIV RNA expression is related to intestinal symptoms, histopathologic alterations, and accelerated disease progression. The localization of HIV to areas of cellular injury will be sought to provide direct evidence of its role in intestinal disease. Studies will involve HIV-infected volunteers with and without symptoms and controls who are followed quarterly and undergo three GI evaluations over two years. Cellular reservoirs and mucosal viral content in mucosa and blood will be determined by RNA in situ hybridization, DNA and RNA template-specific polymerase chain reaction, in situ PCR, electron and immunoelectron microscopy, and immunohistology. Cells undergoing lysis via apoptosis or apparent syncytia formation will be identified and the presence of HIV determined by immunohistochemistry and immunoelectron microscopy. The relative importance of selected cytokines and specific anti-HIV immune functions in modulating mucosal HIV RNA production will be compared and a predictive model for HIV RNA expression derived. Demonstration of the importance of intestinal mucosa in disease progression may lead to better understanding of the mechanisms underlying lymphoid depletion and could lead to new therapeutic strategies.